1. Field of the Invention
This invention relates to improvements in apparatus for evaluating the oxygen saturation of blood and relates more particularly to a class of instruments known as reflectance oximeters. In such instruments an electro-optical system functions to cause light at two preselected different wavelengths to radiate a whole blood sample contained in a cuvette.
2. Discussion of the Prior Art
As is known in the art, one of the two wavelengths selected to be diffusely reflected equally by the oxyhemoglobin and reduced hemoglobin in the blood. The other wavelength of light is selected such that it is reflected efficiently by the oxyhemoglobin and is strongly absorbed by the reduced hemoglobin. The oximeter then compares the values of reflected light at the predetermined wavelengths and according to known equations computes the oxygen saturation of the blood.
One such instrument for the measurement of oxygen saturation in the blood is described in detail in U.S. Pat. No. 3,296,922, assigned to the Assignee of the present application. This patent describes the electro-optical system for determining the relationship of saturations in the blood of the hemoglobin at wavelengths of 660 and 805 millimicrons wherein the light source is an incandescent lamp and various filtering means are used to accomplish the selected light wavelengths for irradiation.
The procedure by which reflected oximetry may be performed is described in U.S. Pat. No. 3,177,757 also assigned to the assignee of the present invention.
With the advance of the electronic arts and the development of light-emitting diodes, it has become advantageous to use independent separate light sources for the preselected wavelengths of light used to irradiate the selected blood samples. The inclusions of such improvements in the art of reflective oximetry are discussed in U.S. Pat. No. 3,647,299. In U.S. Pat. No. 3,647,299, drive circuits for the utilization of light-emitting diodes in reflective oximetry are described in U.S. Pat. No. 3,902,806, both of these identified patents are assigned to the Assignee of the present invention. One of the more recent advances in reflective oximetry has occurred in the area of the development of a disposable cuvette for the use of the clinician in making the oxygen saturation determinations. Since the disposable cuvette has eliminated the need to clean the cuvette including sterilization, the technician may now evaluate a number of blood samples in rapid succession by merely cycling through each sample in its own disposable cuvette.
The present invention is directed to improving the mechanism of the reflective oximeter to take most advantageous use of the disposable cuvette and flexibility of its operation and coordinate that with improving the speed and ease with which oxygen saturation measurements may be made in the oximeter.